U.S. patent application number 13/859643 was filed with the patent office on 2014-10-09 for coherent aggregation from multiple diverse sources on a single display.
This patent application is currently assigned to RAYTHEON COMPANY. The applicant listed for this patent is RAYTHEON COMPANY. Invention is credited to Stefan Badstuebner, Jim L. Booher, Christopher R. Eck, Annette R. Mueller, John A. Schlundt, Ron C. Williamson.
Application Number | 20140300508 13/859643 |
Document ID | / |
Family ID | 51539316 |
Filed Date | 2014-10-09 |
United States Patent
Application |
20140300508 |
Kind Code |
A1 |
Booher; Jim L. ; et
al. |
October 9, 2014 |
COHERENT AGGREGATION FROM MULTIPLE DIVERSE SOURCES ON A SINGLE
DISPLAY
Abstract
A system for tracking objects. Objects such as aircraft, ground
vehicles, or vessels may be sensed with various sensors, including
an Integrated Broadcast Service (IBS) (220), an Advanced Field
Artillery Tactical Data System (AFATDS) (225), a network (230) of
airborne radar sensors, a network (235) of aircraft each reporting
its own position, a Blue Force Tracker (BFT) (240), and a network
(245) of ground-based mobile radar sensors. Data from each sensor
or network of sensors may also be fed, via a display interface
layer (250), to a display. A tracker which may be referred to as a
coherent aggregator (120) receives input from sensors or other
trackers and also from an operator. The operator monitors the
display and provides input to the coherent aggregator (120) to
assist the coherent aggregator (120) in inferring tracks from
measurement reports. Multiple coherent aggregators, in
communication with each other and loosely coupled, may be operated
simultaneously.
Inventors: |
Booher; Jim L.; (Fullerton,
CA) ; Eck; Christopher R.; (St. Petersburg, FL)
; Badstuebner; Stefan; (Brea, CA) ; Williamson;
Ron C.; (Fullerton, CA) ; Schlundt; John A.;
(Fort Wayne, IN) ; Mueller; Annette R.; (Brea,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
RAYTHEON COMPANY; |
|
|
US |
|
|
Assignee: |
RAYTHEON COMPANY
Waltham
MA
|
Family ID: |
51539316 |
Appl. No.: |
13/859643 |
Filed: |
April 9, 2013 |
Current U.S.
Class: |
342/176 |
Current CPC
Class: |
G01S 7/04 20130101; G01S
7/22 20130101; G08G 5/0082 20130101; G01S 13/66 20130101; G08G
5/0021 20130101; G08G 5/0078 20130101; G01S 13/726 20130101 |
Class at
Publication: |
342/176 |
International
Class: |
G01S 7/04 20060101
G01S007/04; G01S 13/66 20060101 G01S013/66 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0001] This invention was made with U.S. Government support under
contract No. M67854-11-C-0205, awarded by the United States Marine
Corps. The U.S. Government has certain rights in this invention.
Claims
1. A system for tracking a plurality of objects, comprising: a data
interface configured to receive a plurality of data elements, each
data element selected from the group consisting of: measurement
reports comprising data about objects; and tracks, comprising
inferred trends in data about objects; a user interface comprising
a display and a user input device, the user interface coupled to
the data interface and configured to display measurement reports
and tracks; and a first coherent aggregator, coupled to the data
interface and to the user interface, the first coherent aggregator
configured to: receive at least one data element; receive user
input from the user input device; generate a revised track in
response to the data element and the user input; and provide the
revised track to the display.
2. The system of claim 1, wherein the data interface is configured
to receive data from an Integrated Broadcast Service (IBS)
sensor.
3. The system of claim 1, wherein the data interface is configured
to receive data from an Advanced Field Artillery Tactical Data
System (AFATDS) system.
4. The system of claim 1, wherein the data interface is configured
to receive data from an airborne radar sensor.
5. The system of claim 1, wherein the data interface is configured
to receive data from an aircraft transmitting its position.
6. The system of claim 1, wherein the data interface is configured
to receive data from a Blue Force Tracker (BFT) system.
7. The system of claim 1, wherein the data interface is configured
to receive data from a ground-based mobile radar sensor.
8. The system of claim 1, wherein the first coherent aggregator is
a battle control system (BCS).
9. The system of claim 1, wherein the first coherent aggregator is
an Enhanced-OASIS Fusion Capability (E-OFC) system.
10. The system of claim 1, wherein the user interface is configured
to enable a user to designate two icons corresponding to two tracks
to be merged into one track.
11. The system of claim 1, wherein the first coherent aggregator is
configured to receive user input comprising instructions to merge
two tracks into one track.
12. The system of claim 1, wherein the first coherent aggregator is
configured to receive user input comprising instructions to
interchange two tracks.
13. The system of claim 1, comprising a second coherent aggregator,
loosely coupled to the first coherent aggregator, and configured to
communicate with the first coherent aggregator.
14. A method for tracking a plurality of objects, comprising:
receiving a data element selected from the group consisting of:
measurement reports comprising data about objects; and tracks,
comprising inferred trends in data about objects; receiving user
input; generating a revised track in response to the data element
and the user input; and providing the revised track to a
display.
15. The method of claim 14, wherein the receiving of user input
comprises: displaying a plurality of tracks on the display;
enabling a user to select two tracks; and enabling a user to
provide, as user input, an instruction to merge the two selected
tracks.
16. The method of claim 15, wherein the enabling of the user to
select two tracks comprises enabling the user to left click on a
first one of the two tracks and enabling a user to right click on a
second one of the two tracks.
17. The method of claim 15, wherein the enabling of the user to
select two tracks comprises enabling the user to drag a rectangle
containing the two tracks.
18. The method of claim 14, comprising displaying information about
an object of the plurality of objects.
Description
BACKGROUND
[0002] 1. Field
[0003] One or more aspects of embodiments according to the present
invention relate to sensing objects using sensors or networks of
sensors, and inferring trends, which may also be referred to as
tracks, in the motion of the objects.
[0004] 2. Description of Related Art
[0005] Systems for tracking objects such as aircraft, ground
vehicles, and vessels, may be constructed using various sensors and
other means for detecting, identifying, and locating such objects.
Sensors may use radar, for example, or video images, or in some
cases an object may transmit electromagnetic radiation,
intentionally or unintentionally providing information about the
object.
[0006] A system for tracking such objects, which may also be
referred to as a tracker, may periodically obtain measurement
reports from one or more sensors, and the tracker may employ
various algorithms to attempt to fuse the measurement reports into
tracks, i.e., trends in the measurement reports, indicating for
example the path over which an object has traveled. To form tracks,
the tracker may make fusion decisions, including decisions about
which set of measurement reports to fuse into a track. In some
circumstances, these fusion decisions may be error-prone. A
higher-level tracker, which may be referred to as a system tracker,
may receive tracks from trackers and fuse them to form improved
tracks.
[0007] Sensor systems are subjects of ongoing technological
development and engineering, and as a result new sensor systems or
capabilities become available from time to time. Modifying a
tracker to accept data from a new sensor, or new data from an
existing sensor, may be time-consuming and may involve a long
development cycle. Thus, there is a need for a system for tracking
objects capable of rapidly taking advantage of changes in sensors,
and with reduced vulnerability to errors.
SUMMARY
[0008] In one embodiment, a system tracker may receive input from
an operator and the operator input may assist the system tracker in
making fusion decisions. Such a system tracker may be referred to
as a coherent aggregator, providing a coherent set of tracks from
various inputs.
[0009] According to an embodiment of the present invention there is
provided a system for tracking a plurality of objects, including: a
data interface configured to receive a plurality of data elements,
each data element selected from the group consisting of:
measurement reports including data about objects; and tracks,
including inferred trends in data about objects; a user interface
including a display and a user input device, the user interface
coupled to the data interface and configured to display measurement
reports and tracks; and a first coherent aggregator, coupled to the
data interface and to the user interface, the first coherent
aggregator configured to: receive at least one data element;
receive user input from the user input device; generate a revised
track in response to the data element and the user input; and
provide the revised track to the display.
[0010] In one embodiment, the data interface is configured to
receive data from an Integrated Broadcast Service (IBS) sensor.
[0011] In one embodiment, the data interface is configured to
receive data from an Advanced Field Artillery Tactical Data System
(AFATDS) system.
[0012] In one embodiment, the data interface is configured to
receive data from an airborne radar sensor.
[0013] In one embodiment, the data interface is configured to
receive data from an aircraft transmitting its position.
[0014] In one embodiment, the data interface is configured to
receive data from a Blue Force Tracker (BFT) system.
[0015] In one embodiment, the data interface is configured to
receive data from a ground-based mobile radar sensor.
[0016] In one embodiment, the first coherent aggregator is a battle
control system (BCS).
[0017] In one embodiment, the first coherent aggregator is an
Enhanced-OASIS Fusion Capability (E-OFC) system.
[0018] In one embodiment, the user interface is configured to
enable a user to designate two icons corresponding to two tracks to
be merged into one track.
[0019] In one embodiment, the first coherent aggregator is
configured to receive user input comprising instructions to merge
two tracks into one track.
[0020] In one embodiment, the first coherent aggregator is
configured to receive user input comprising instructions to
interchange two tracks.
[0021] In one embodiment, the system includes a second coherent
aggregator, loosely coupled to the first coherent aggregator, and
configured to communicate with the first coherent aggregator.
[0022] According to an embodiment of the present invention there is
provided a method for tracking a plurality of objects, including:
receiving a data element selected from the group consisting of:
measurement reports including data about objects; and tracks,
including inferred trends in data about objects; receiving user
input; generating a revised track in response to the data element
and the user input; and providing the revised track to a
display.
[0023] In one embodiment, the receiving of user input includes:
displaying a plurality of tracks on the display; enabling a user to
select two tracks; and enabling a user to provide, as user input,
an instruction to merge the two selected tracks.
[0024] In one embodiment, the enabling the user to select two
tracks includes enabling the user to left click on a first one of
the two tracks and enabling a user to right click on a second one
of the two tracks.
[0025] In one embodiment, the enabling of the user to select two
tracks includes enabling the user to drag a rectangle containing
the two tracks.
[0026] In one embodiment, the method includes displaying
information about an object of the plurality of objects.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Features, aspects, and embodiments are described in
conjunction with the attached drawings, in which:
[0028] FIG. 1 is a block diagram of a coherent aggregator coupled
to several trackers and to a display according to an embodiment of
the present invention;
[0029] FIG. 2 is block diagram of two coherent aggregators coupled
to trackers and sensor networks and to a display according to an
embodiment of the present invention;
[0030] FIG. 3 is a screen shot of a display according to an
embodiment of the present invention;
[0031] FIG. 4 is a screen shot of a display according to another
embodiment of the present invention; and
[0032] FIG. 5 is a flow chart of a method for tracking objects
according to an embodiment of the present invention.
DETAILED DESCRIPTION
[0033] The detailed description set forth below in connection with
the appended drawings is intended as a description of exemplary
embodiments of a method for coherent aggregation from multiple
diverse sources on a single display provided in accordance with the
present invention and is not intended to represent the only forms
in which the present invention may be constructed or utilized. The
description sets forth the features of the present invention in
connection with the illustrated embodiments. It is to be
understood, however, that the same or equivalent functions and
structures may be accomplished by different embodiments that are
also intended to be encompassed within the spirit and scope of the
invention. As denoted elsewhere herein, like element numbers are
intended to indicate like elements or features.
[0034] Referring to FIG. 1, in operation a system for tracking
objects may include a number of sensors 105, each providing
individual measurements which may be referred to as measurement
reports. Each measurement report contains information about an
object, taken at a point in time, or over a short interval of time.
A measurement report may indicate the position and velocity of an
object, and it may contain identifying information about the
object. For example, a tracked object may be equipped with a Global
Positioning System (GPS) receiver and a radio transmitter, and it
may periodically transmit the tracked object's position to a
receiver. The receiver in this case may act as a sensor 105. Some
sensors, e.g., sensors in the Integrated Broadcast Service (IBS)
may obtain information about objects by receiving communications
transmitted by the objects. Such sensors may, for example, provide
relatively accurate identifying information about tracked objects
while providing relatively inaccurate position information. Other
sensors, such as radar systems, may provide relatively accurate
position information while providing less accurate identifying
information.
[0035] It may be advantageous to aggregate, or fuse, multiple
measurement reports into inferred trends, or time records of
position, which may be referred to as tracks. For example, if a
radar system has an aircraft in its field of regard, and forms a
new observation of the aircraft every second, then the sequence of
locations spaced one second apart forms a track which may also
contain estimates of the current and past locations of the
aircraft. The track is readily inferred by a human observer
presented with consecutive dots on a screen, or by a computer which
may connect consecutive observations in time-order to estimate the
track position at any time in the past, current, and future. An
automated system for inferring such a track from measurement
reports may be referred to as a tracker.
[0036] If two aircraft are within the radar's field of regard, the
problem of reconstructing or inferring a track for each aircraft
may be more challenging, especially if the aircraft are near each
other and if the aircraft are maneuvering. If a sufficiently long
time interval elapses between measurement reports, then it may be
difficult to determine which of two objects in a current set of
measurement reports corresponds to which of the objects in
previously obtained measurement reports. A tracker 110 may maintain
a set of alternate hypotheses about candidate tracks, each
candidate track fusing multiple measurement reports, and it may
rank the hypotheses according to their likelihood in light of
received measurement reports. The likelihood of a hypothesis may be
influenced by uncertainty in a type identification, or by the
degree of confidence in a position measurement, which in some
embodiments may be characterized by an uncertainty ellipse.
[0037] A tracker 110 may receive measurement reports and create new
or update existing tracks from them, making fusion decisions to do
so, or it may also receive tracks from other trackers, in which
case the tracker 110 may be referred to as a system tracker. For
example, a system tracker may receive tracks from a first tracker
using ground-based radar sensors, and from a second tracker using
airborne radar sensors, and the system tracker may make fusion
decisions to infer, for example, that a track received from the
first tracker corresponds to the same physical object as a track
received from the second tracker, i.e., that the two tracks
received are better represented as a single track. By combining
overlapping information from multiple sensors 105 or multiple
trackers 110, a tracker or system tracker may produce more accurate
or more reliable tracks.
[0038] A sensor 105 may be able to provide various types of
information about a tracked object, such as what the platform of
the object is, e.g., a particular type of vehicle, vessel, or
aircraft. For example, radar returns from an aircraft may contain a
characteristic signature which may indicate the type of engine or
engines on the aircraft, in some cases making it possible to
identify the model of aircraft. Such an identification may also be
helpful in making fusion decisions in a tracker, which may have
different models for possible behaviors, and use a model
corresponding to the object's platform.
[0039] When sensor technology changes, e.g., as new types of sensor
become available, or when existing sensors are upgraded with new
capabilities, integrating the new sensors or sensor capabilities
into existing trackers may be costly and time-consuming, because of
the complexity of tracker algorithms, which result in a long
development cycle.
[0040] Referring still to FIG. 1, in one embodiment, a system
tracker is integrated with a user interface 115 allowing it to
interact with an operator. In this configuration, i.e., when
configured to accept input for use in making fusion decisions, from
a human operator, the system tracker may be referred to as a
coherent aggregator 120. A human operator may in some respects be
able to make better fusion decisions than a tracker, and may
instruct the tracker, using one or more operator input devices 130,
to correct erroneous fusion decisions. Input devices 130 may
include, for example, a keyboard and a mouse.
[0041] For example, a human operator may possess information, which
may be referred to as general intelligence information, about the
situation being observed, not readily supplied to a tracker.
General intelligence information may include, for example,
knowledge of the dispositions of enemy forces, e.g., the location
of enemy bases from which enemy aircraft may approach, and
familiarity with past behaviors of enemy forces. For example, an
operator may be in communication with a friendly aircraft
dispatched to intercept a hostile aircraft, and when the
interceptor draws near to the hostile aircraft, both aircraft may
begin to maneuver to avoid each other. In a situation with two
aircraft near each other, both maneuvering rapidly, a tracker 110
may be particularly likely to err in identifying which object is
the friendly aircraft and which is the hostile aircraft. The
operator, however, may be able, by communicating with the
interceptor pilot, to correctly identify the objects.
[0042] In one embodiment, a display may be configured to display a
variety of tracks or measurement reports, or both, and a coherent
aggregator 120 may be configured to accept input from a human
operator, the input allowing the coherent aggregator 120 to make
improved fusion decisions. For example, if a coherent aggregator
120 incorrectly labels a friendly aircraft as hostile, and vice
versa, the operator may instruct the coherent aggregator 120 to
correct the error. In another example, the coherent aggregator 120
may be generating two tracks near each other, e.g., apparently made
by two aircraft flying close together, but the tracks may in fact
correspond to only one physical object, observed for example by
several independent sensors 105. In this case an experienced human
operator may have general intelligence information allowing the
operator to determine that what is displayed as two tracks should
be displayed as a single track, and the operator may instruct the
coherent aggregator to merge the tracks. In another example an
operator may realize that the coherent aggregator 120 has
incorrectly fused the tracks of two different objects, displaying
them as a single track, and the operator may instruct the coherent
aggregator 120 to treat the track as two separate tracks. In
another example, an operator may know, e.g., from the disposition
of enemy forces, that a platform identification a coherent
aggregator 120 has made is incorrect, and the operator may instruct
the coherent aggregator 120 to correct it. A human operator also
may be able to learn fairly quickly to use data from a new sensor
105.
[0043] Interactions between an operator and a tracker 110 or
coherent aggregator 120 may also be advantageous in other
situations. In one example, a hostile aircraft may be equipped with
a modified transponder causing it to transmit an identification
number, which may be referred to as a tail number, belonging to a
commercial aircraft, and the hostile aircraft may be flying along a
path normally flown by commercial aircraft. A tracker 110
monitoring the locations of commercial aircraft, for example using
transponder returns or filed flight plans, may have a database of
aircraft and their locations, and it may display these locations,
along with the tail number, to the operator. The operator may
discover that the tail number reported by the hostile aircraft
belongs to an aircraft the location of which is also reported to be
elsewhere, and, in response, the operator may identify the hostile
aircraft as suspect, using an operator input device in the user
interface. In one embodiment, the tracker 110 assists the operator
by displaying duplicate tail numbers in a particular color, drawing
the operator's attention to them. As indicated by the dashed arrow
of FIG. 1, in some instances a tracker may send information only to
the display, and not to the coherent aggregator.
[0044] A system in which an operator participates or assists with
fusion decisions may also be advantageous in reducing the time
required to begin using a new sensor, or a new capability of an
existing sensor. In one embodiment, raw measurement reports from
the new sensor are sent directly to a display in a user interface,
and displayed as points, identified for example by an icon 310
(FIG. 3) corresponding to the new sensor or by an icon representing
some characteristic detected by the sensor, such as the platform
type. The ability to display such icons 310 may be implemented
using a relatively thin layer of interface software, which may be
referred to as a display interface layer 250 (FIG. 2), costing
considerably less than the integration of the new sensor or
capabilities into a tracker, which may have a long development
cycle. The operator may then use the newly available information to
help guide fusion decision feedback provided by the operator to the
coherent aggregator 120. In one embodiment, input from an operator
is treated by a coherent aggregator as being highly reliable.
[0045] The trackers in the embodiment of FIG. 1 may also be
equipped with engineering displays 160, which may display
measurement reports or tracks, and which may be helpful for
troubleshooting.
[0046] Referring to FIG. 2, in one embodiment two coherent
aggregators 120, a battle control system (BCS) 210 and an
Enhanced-OASIS Fusion Capability (E-OFC) system tracker 215 are
each connected to several of a set of sensors or sensor networks,
including an IBS 220, an Advanced Field Artillery Tactical Data
System (AFATDS) 225, a network 230 of airborne radar sensors, a
network 235 of aircraft each reporting its own position, a Blue
Force Tracker (BFT) 240, and a network 245 of ground-based mobile
radar sensors. Data from each sensor or network of sensors may also
be fed, via a display interface layer 250, to the display.
[0047] The two coherent aggregators 120 may also communicate
directly with each other. The coherent aggregators 120 may, for
example, exchange tracks and track identifiers, allowing each
coherent aggregator 120 to build a list of cross-references, in
which its tracks are associated, by track identifier, with tracks
received from the other coherent aggregator 120, in cases in which
the tracks appear to correspond to the same physical object. The
coherent aggregators 120 in an embodiment such as that of FIG. 2
may be complementary in the sense that the AFATDS 225 may provide
relatively reliable identification information with relatively
inaccurate position information and the network of ground-based
mobile radar sensors 245 may provide relatively high accuracy
position information with relatively poor identifying information.
Similarly, one coherent aggregator 120, such as an E-OFC coherent
aggregator 215, may provide relatively reliable identification
information with relatively inaccurate position information, and
another coherent aggregator 120, such as a BCS coherent aggregator
210, may provide relatively high accuracy position information with
relatively poor identifying information. The two coherent
aggregators 120 may be loosely coupled, which, as used herein,
means that each coherent aggregator 120 has, or makes use of,
little or no knowledge of the definitions of other separate
coherent aggregators 120.
[0048] Referring to FIG. 3, in one embodiment a display may show,
on a background representing a geographical area, a plurality of
icons 310, each representing a tracked object. Icons 310 with
different shapes may be used to represent ground vehicles, vessels,
and aircraft, and different colors may be used to identify the
objects as friendly, hostile, or suspect. Lines, or shapes formed
from lines, referred to as geometries 320, may provide additional
information to an operator viewing the display. For example, an
ellipse 325 formed from a dashed line may be used to indicate that
several objects within the ellipse are associated, e.g., they are a
group of aircraft flying a resupply mission. A geometry 320 may
also identify a boundary between geographic regions, a forward line
of troops, or the like.
[0049] Using the display and an input device such as a mouse, an
operator may designate two objects and execute a merge command to
instruct the coherent aggregator(s) 120 that provided the tracks to
merge the tracks corresponding to the two displayed objects into a
single track, the operator having determined that the two displayed
objects in fact correspond to a single physical object. To
designate two objects, the operator may, for example, select a
first object by left clicking on the corresponding icon, and then
select a second object by right-clicking on it, or the operator may
select both objects by dragging the mouse diagonally, which may
result in the user interface displaying a rectangle with one corner
at the location at which a mouse button was first pressed, and with
the diagonally opposite corner at the current mouse location, or at
the location at which the mouse button was released. Every object
in the rectangle may become selected as a result. When an object is
selected, the display may show a selected object identifier, such
as a circle 330 or square 335 centered on the selected object. At
the same time, the display may show an information box 340
containing information about the object, including, for example, a
track identifier, the current location of the object, whether it is
friendly, the type of platform, and its velocity. The track
identifier may indicate the source of the data for the object,
e.g., the track identifier may be an alphanumeric string with
initial characters identifying a sensor network or tracker 110 that
generated the position data for the object. The act of selecting an
object may also be referred to as hooking the object.
[0050] In another example, if the operator has selected more than
two objects, e.g., by drawing a rectangle including more than two
objects, an information box 340 may be shown listing a number of
selected objects, from which the operator may select two, on which
to execute the merge command. The operator may be able to execute a
merge command in any of several ways, including selecting a merge
option from a drop-down menu which may be displayed in response to
a right mouse click, or from a menu or submenu available at the top
of the display window.
[0051] Referring to FIG. 4, in one embodiment, the display may show
a simulated perspective view of a geographic area, with tracked
objects represented by icons 310 drawn to approximate the shape of
the object identified, with an aircraft shown as a shape resembling
an aircraft, for example, and a ground vehicle shown as a shape
resembling a ground vehicle. Both in the embodiment illustrated in
FIG. 3, and in this embodiment, the operator may select several
objects and instruct the coherent aggregator(s) 120 that provided
the tracks to merge them, select two objects and instruct the
coherent aggregator(s) 120 that provided the tracks to interchange
their identities, or select one object and instruct the coherent
aggregator 120 that provided the track to separate it into two.
[0052] Referring to FIG. 5, acts involved in practicing an
embodiment of the present invention may be illustrated with a flow
chart. In an act 510 a coherent aggregator 120 receives at least
one data element, where a data element may be a measurement report
or a track. In an act 515 the coherent aggregator 120 receives user
input, for example an instruction to merge two tracks. In an act
520, the coherent aggregator 120 revises at least one track in
response to the received user input, and in an act 525, the
coherent aggregator 120 displays the revised track, i.e., provides
the revised track to a display device.
[0053] Although limited embodiments of a method for coherent
aggregation from multiple diverse sources on a single display have
been specifically described and illustrated herein, many
modifications and variations will be apparent to those skilled in
the art. Accordingly, it is to be understood that the method for
coherent aggregation from multiple diverse sources on a single
display employed according to principles of this invention may be
embodied other than as specifically described herein. The invention
is also defined in the following claims, and equivalents
thereof.
* * * * *